1. Field of the Invention
The present invention relates to on-site wastewater (sewage) treatment systems and processes, and more particularly to a stand-alone aerobic treatment unit or pod system for promoting oxygen transfer and aerobic bacterial activity in conjunction with conventional septic tank systems for family residences and commercial establishments.
2. Description of the Prior Art
At present, many single and multiple family dwelling units as well as small commercial installations rely upon the well known process of wastewater (sewage) disposal involving a septic tank and drain field installation. In these installations the biodegradable wastewater contains a wide variety of solid and liquid materials which are introduced directly from the source into a septic tank for primary treatment. The septic tank itself functions as a settling chamber in which the solids are allowed to settle out in a quiescent zone with both liquids and solids being subjected to digestion exclusively by anaerobic micro organisms. The anaerobic liquor or effluent, free of most solids, is then discharged directly into a drain field for final disposal. One common form of septic tank system includes at least two chambers with the primary chamber receiving the raw wastewater where the solids are allowed to settle to the bottom. The liquor then transfers to a second chamber where further settling and anaerobic digestion is allowed to proceed. The effluent then drains off to a drain field. The anaerobic treatment system is extremely slow compared to aerobic processes whereby oxygen is introduced and absorbed into the wastewater so that aerobic micro organisms are relied upon to provide aerobic metabolism of sewage organics. The aerobic system of sewage treatment is not only more rapid than anaerobic treatment but also eliminates offensive odors and oft times pollution of the environment caused by odiferous insufficiently treated wastewater from aging or overloaded septic tank systems. A multitude of systems have been proposed in the prior art for increasing the efficiency and effectiveness of septic tank systems in the nature of chemical treatment plants, filter systems and secondary sewage treatment systems for aeration of the liquids discharged, either from the septic tank or directly from the source. Filter systems and/or chemical treatment processes have been used for both large and smaller installations, however, such systems tend to be complex, expensive to install, unreliable and difficult to maintain. Examples of prior art secondary sewage treatment systems using aeration and aerobic bacterial growth media are disclosed in U.S. Pat. Nos. 5,030,353; 5,200,081; 5,202,027; and 5,609,754.
In some instances, reactors containing microbial growth media and/or filtering devices incorporating aeration features to treat the liquid effluent have been proposed for use in conjunction with septic tanks. One example of this type of device may be found in U.S. Pat. No. 5,554,996. In this type of device, air is diffused into a reactor chamber so as to cause liquor to recirculate within the reactor chamber in the presence of microbial growth media with the reactor chamber being connected directly to the outflow of the treatment tank. Thus, only the liquor-effluent within the reactor chamber is being aerated and mixed, leaving the balance of the volume within the settlement tank untreated. The major part of the septic tank thus remains anaerobic with the usual inefficient and slow odor producing decomposition attendant standard septic tank systems. In addition, all wastewater entering the septic tank must pass through the reactor chamber on its way to the outlet of the tank. The volume of liquor treated is thus limited and frequent clogging of the media and/or filter system may occur with ultimate failure of the tank system during overload periods or after long use. Systems of this type may also employ pumping devices which must be regulated in such a manner as to accommodate variations in flow volume and timed dosing, resulting in frequent failures and a fluctuating liquid depth within the septic tank. Since all sewage is not created equal and may vary widely over any given time period in terms of strength, volume and composition, these shortcomings are of great concern.
In view of the foregoing, there remains a continuing need for a system with greater efficiency and reliability for the treatment of wastewater and sewage in primary treatment systems such as standard septic tanks of all configurations as well as other traditional anaerobic digestion systems. To be successful, the system must be of a nature that is adaptable for retrofitting existing septic tank systems of all sizes and have the ability to increase the dissolved oxygen content of the otherwise anaerobic liquor so as to promote aerobic microbial digestion processes in the entire tank volume. Expensive pumping systems and dosing mechanisms which require constant maintenance must be avoided. There is also a need for the ability to back-flush and clear the microbial growth medium of organic build up to prevent clogging and to increase effectiveness without extensive reworking or modification of the system. Back flushing may also be used in situations where the unit is organically overloaded and additional air entrainment points are required to increase the available oxygen necessary for treatment. In order to provide for increased usage or loading of the septic system, provision must also be made for increasing or decreasing the treatment units within an existing septic system without major overhaul or reworking of the existing septic system.